Aerosol containers of this type are illustrated, for example, in Japan Utility Model Publication No. 1,474/70 and Japan Patent Kokai No. 11,673/83.
The aerosol container disclosed in Japan Utility Model Publication No. 1,474/70 uses silicone rubber as sealant for the sliding contact section in order to compensate the inferior gas-barriering ability of the piston means (i.e. slidable plate) with the purpose of stopping the leakage of a liquefied gas from the propellant area into the propellant area through a narrow gap, i.e. sliding contact section, located between a piston means and the inside wall of the container. Silicon rubber, however, has its disadvantages that it is insufficient in gas-barriering ability and hinders the piston means to move smoothly, as well as additional disadvantages that it deteriorates rapidly and does not endure prolonged use.
Japan Patent Kokai No. 11,673/83 teaches the use of lubricants such as white petrolatum, grease or palm oil as sealant for the sliding contact section in place of silicone rubber, and it is reported that these lubricants exhibit satisfiable sealing effect. It was confirmed that such lubricants, however, dissolve the liquefied gas used as propellant, resulting in an imperfect sealing and eventually in the leakage of the propellant into product area within a short period of time.
Japan Patent Kokai No. 11,673/83 also teaches a procedure to manufacture aerosol container comprising the steps of filling a product while keeping the bottom of a container body having a spout (e.g. nozzle) upward, inserting the first slidable plate (e.g. piston means), sealant and the second slidable plate (e.g. piston means) in the give order into the container body, filling a propellant as injection agent, and sealing the open end of the container body. Such procedure to manufacture aerosol container, however, has the following disadvantages:
(1) In such procedure including the steps of first filling a liquefied gas as propellant while leaving the propellant area of the container open, then sealing the opening, it is not desirable to seal at normal temperature and pressure because of the vigorous evaporation of the liquefied gas during the sealing step. Accordingly, the sealing step should be carried out at a very low temperature, e.g. -40.degree. C. or lower, wherein the liquefied propellant gas is still in liquid form. Furthermore, such procedure is not feasible for a compressed propellant gas.
(2) In such procedure including the steps of first filling the product in the container body while keeping its bottom upward, then inserting the slidable plate (e.g. piston means) into the container body, a small portion of air present between the product and the slidable plate may be incorporated into the product, resulting in the occurrence of inferior products.
(3) Since such procedure requires filling of the product in the course of manufacturing the container per se, container manufacturers were required to install an appropriate filling system, otherwise aerosol product manufacturers were required to install a container manufacturing system.
It is very difficult to smoothly practice such procedure because the techniques for manufacturing aerosol container and for filling product into such container belong to entirely different technologies.
Desirably, it is much more practicable that the container manufacturer takes the responsibility of producing containers and supplying them to aerosol product manufacturer, and that the aerosol product manufacturer takes the responsibility of filling his product and a propellant to manufacture aerosol products.